At a webmaster point of view, if there was ever a security breach for whatever reason, and users system wide needed to change their passwords for example, we would need to be able to message our Users. By my understanding of the law, you don't need an opt-out to send such emails, but out of respect we could implement safeguards to users wishing not to get anything.
Perhaps a subscription option could be added to user management? Having an opt-out for Mailing List, and another Opt-Out for ALL mail. Users could select at signup or in their settings. Just a suggestion, so both sides perhaps come out happy?
